The present invention relates to a hub for at least partially muscle-powered vehicles and in particular for two-wheeled vehicles. Such a hub comprises a fixed hub axle, a hub body rotatable relative thereto, a rotatable driving device, and a toothed disk freewheel. The driving device may for example be configured as a rotor to which at least one sprocket or else a set of sprockets can be mounted for transmitting the driving torque via the driving device to the hub body. Optionally the driving device may be configured integrally with a sprocket or a set of sprockets.
In DE 20 2011 108 822 U1, a hub construction has been disclosed wherein, instead of axial toothings, an annular driving component and a passive component are provided. At the annular driving component a conical first ratchet is formed which is provided with a pair of triangular contact areas forming a conical surface in the radial direction. The passive component is formed provided with a conical second ratchet. The cone-type shape of the ratchets is intended to reduce friction in axial displacement. For biasing the passive component and the driving component to engagement with one another, two pairs of annular magnets may be provided with the magnetic rings of a pair repelling one another, thus urging the passive component and the driving component toward one another. In the alternative, coil springs may be provided for urging the driving component and the passive component toward one another. The drawback of the hub is that the hub construction with the magnetic rings is comparatively heavy. Using coil springs allows a lower weight. While the conical ratchets allow to optionally reduce the friction in axial displacement, this also reduces the area of engagement as the driving component and the passive component move just a little away from one another. This may impede, or turn insufficient, the responsivity in relation to the force relationships. However, with the biasing force increased, the friction in the freewheeling state will increase in turn. This design does allow a reduction in friction at the outer diameter. However, precise guidance is required, thus increasing friction at the inner diameter to allow an operationally reliable solution.
EP 2 422 996 A1 discloses a rear wheel hub for a bicycle in which a freewheel is provided between the rotor and the hub shell. The freewheel comprises an axial toothing at the rotor and a toothed disk that is axially movably and non-rotatably received in the hub shell, with an axial toothing that is biased by two annular permanent magnets to the engaging position with the axial toothing at the rotor. According to EP 2 422 996 A1, the maintenance-free construction of this design is an advantage. The magnetic biasing device applies a reproducible force on the movable toothed disk at all times, independently of mechanical properties. EP 2 422 996 A1 shows the basic drawback, however, that the strength of the magnetic field and thus the strength on the movable toothed disk decreases with the distance between the two permanent magnets. In the freewheel position, the two permanent magnets are disposed particularly closely to one another such that a relatively high force urges the toothed disk to the engaging position. Although this results in fast responsivity, there is the drawback of increased friction in the freewheeling state. Moreover, the gliding of the axial toothings on one another in the freewheeling state emits loud noises. In the engaged state, the acting biasing force is considerably lower though since the distance between the two permanent magnets is considerably larger. This may be disadvantageous to the reactivity of the freewheel in or close to the engaged state in particular when the axial toothing of the toothed disk is only just not yet engaged with the axial toothing at the rotor.